PET wear layer/sol gel top coat layer composites

ABSTRACT

Composite wear layers that include a polyethylene terephthalate wear layer adhered to an organic/inorganic (O/I) top coat layer, and surface coverings and surface covering components including the composite wear layers, are disclosed. The organic/inorganic top coat layer is formed from a top coat formulation that comprises a coupling agent that includes an organic polymerizable moiety such as epoxy, acrylate and the like, as well as an inorganic polymerizable moiety such as a silanol. The wear layer is typically in the range of about 1-20 mils thickness, and the top coat layer is typically in the range of 2 microns to 0.5 mils thickness. The composite wear layers can be included in surface coverings or surface covering components, such as floor and wall coverings. An adhesion promoter/binder can be used to better adhere the polyethylene terephthalate wear layer to the organic/inorganic top coat layer.

FIELD OF THE INVENTION

The present invention relates generally to composite wear layers forsurface coverings. In particular, the invention relates to a compositewear layer for a surface covering, composite comprises a polyethyleneterephthalate (PET) wear layer adhered to an organic/inorganic top coatlayer.

BACKGROUND

The flooring industry has been working to develop wear layer systems andflooring products incorporating these systems which provide excellentgloss retention & scratch resistance. For non-residential (commercial)flooring applications such as use in schools, hospitals, stores, etc.wherein the composite wear layer must also provide excellent colorstability over the lifetime of the product due to exposure to light andas well as excellent stain resistance from foot traffic conditions.Additionally, the composite wear layer must also be compatible withmaintenance materials that can be applied after some wearing of thecomposite wear layer occurs.

U.S. Pat. No. 5,120,811, the contents of which are hereby incorporatedby reference, discloses using organic/inorganic (O/I) top coat layerswhich provide stain and gloss protection when applied over a clear,protective layer. However, the '811 patent does not describe compositesincorporating the organic/inorganic top coat layer with a composite wearlayer so that it can be used in commercial flooring applications as wellas residential applications.

Current compositions and methods fail to provide top coat layers, andflooring products incorporating the top coat layers, which fully satisfythe foregoing criteria. Accordingly, a need exists for such flooring.

SUMMARY OF THE INVENTION

Composite wear layers that comprise a polyethylene terephthalate wearlayer adhered to an organic/inorganic top coat layer, and surfacecoverings and surface covering components comprising the wear layers,are disclosed. The organic/inorganic top coat layer is formed from a topcoat formulation which includes a coupling agent. The coupling agent isa molecule which includes an organic polymerizable moiety such as epoxy,acrylate and the like, as well as an inorganic polymerizable moiety suchas a silanol. Top coat layers formed from the top coat formulation haveboth organic and inorganic character. Although not limited to thesethickness ranges, the wear layer is typically in the range of about 1-20mils thickness, and the top coat layer is typically in the range ofabout 2 microns to about 0.5 mils thickness.

The composite wear layers can be included in surface coverings orsurface covering components, such as floor and wall coverings. Thesurface coverings can include additional layers, for example, asubstrate, a design layer, a foam layer and the like, directly orindirectly underlying the wear layer. Ideally, any layer directlyunderlying the polyethylene terephthalate wear layer adheres well to thewear layer.

In some embodiments, an adhesion promoter/binder is included to betteradhere the polyethylene terephthalate wear layer to theorganic/inorganic top coat layer. Adhesion promoters are well known tothose of skill in the art, and any adhesion promoter that adequatelyadheres the top coat layer to the wear layer can be used. In someembodiments, hard particles, for example, aluminum oxide particles, areincluded in the top coat layer.

The present invention, and embodiments thereof, are described in moredetail below. Although the present invention has been described withreference to certain embodiments, other embodiments may achieve similarresults and advantages. Variations and modifications of the presentinvention will be apparent to one skilled in the art and the disclosureherein is intended to cover all such modifications and equivalents.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 and 2 are cross-sectional views of two embodiments of the floorproduct described herein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a solution to the problem of providingtop coat layers and surface coverings with excellent gloss retention andscratch resistance, as well as excellent light stability and stainresistance. The solution is in the form of composite wear/top coatlayers, where the wear layer is a polyethylene terephthalate (PET) filmand the top coat layer is an organic/inorganic polymer, where there isadequate interlayer adhesion between the top coat and the wear layers.The composite wear/top coat layers can be included in surface coveringsand surface covering components. In one embodiment, the surface coveringincludes a substrate, a PET wear layer and an organic/inorganic top coatlayer adhered to the PET layer.

The present invention advances building and flooring materials art byproviding a hard wear surface with excellent light stability, stainresistance and gloss protection which can be bonded over a PET wearlayer. Since these transparent polymer/glass (organic/inorganic)compositions can be applied over clear, protective layers, there can bea wide range of applications for a wear surface which will not detractfrom the appearance of the support or surface being protected.

The inorganic/organic hybrids have advantages in that they can beapplied as relatively thin coatings (about 0.1-0.5 mils), require modestcure energy, and exhibit outstanding performance as wear surfaces inflooring applications. Coating thicknesses of about 2-4 microns haveproven to be especially outstanding in physical property tests whenapplied over flooring substrates. The top coat layers are typically veryhard, with MOHS hardness ratings of about 1.75-4. While the hardness istypically less than that of ceramic surfaces, the hardness tends to behigher than normal “hard” polymers such as polymethyl methacrylate(PMMA), which has a MOHS hardness of 1.50. Top coat layers which arebetween about 13 microns and about 2 microns thick can have stainresistance and wear retention which rivals ceramic tile.

It is important that in surface coverings and surface coveringcomponents including the wear layer and a substrate layer and/or a topcoat layer, there is adequate interlayer adhesion to the underlyingsubstrate layer and/or overlying top coat layer. As used herein, theorganic/inorganic top coat layer is adequately adhered to the PET wearlayer when the composite 1) passes cross hatch adhesion, a standardtest—ASTM D-3359, and 2) the top coat layer does not release from thewear layer when abraded, i.e., when walked upon and scratched asdescribed in U.S. Pat. Nos. 5,843,576; 5,663,003; and 5,188,876.

Polyethylene Terephthalate (PET)

Polyethylene terephthalate is a well known polymer. When used to formthe composite layers described herein, it is typically applied in theform of a film, optionally coated with an adhesion promoter to promoteadhesion to a substrate and/or to the organic/inorganic top coat layer.Suitable PET films can be obtained from several sources which includeMitubishi Polyester Films LLC, and Dupont Teijin Films. Additionally,PET copolymer films can also be used, such as PETG. Copolymer films canbe used as long as the majority of the film composition comprises PETunits. These films can be used in thicknesses of about 1 to 20 mils andshould be sufficiently transparent to see the design and color of theflooring substrate below. Suitable PET films which have been evaluatedinclude Melinex 617/500, Melinex 725/500 and Melinex 582/400) (all fromDupont Teijin Films), where the 500 and 400 relate to differentthicknesses of the PET film (5 and 4 mils respectively), and the 617,725 and 582 relate to relate to the adhesion promoter used.

Adhesion Promoters

In some embodiments, no adhesion promoter is required to adhere the PETwear layer to the organic/inorganic top coat layer. While not wishing tobe bound by a particular theory, it is believed that residual reactivefunctional groups on the PET wear layer form can form bonds with theorganic/inorganic top coat layer as the top coat layer is cured (i.e.,polymerized). However, in some embodiments, it may be advisable to usean adhesion promoter to provide adequate interlayer adhesion between thewear layer and the top coat layer.

Any adhesion promoter commonly used to adhere top coat layers and wearlayers can be used. Such adhesion promoters are well known to those ofskill in the art and need not be discussed in depth here. DUPONT TEIJINFILM's 725, 582, 6445 and 617 primers are examples of acceptable primersthat can be used depending upon the organic/inorganic top coatingcomposition. Additionally, primers may also be used on the other side ofthe PET film to improve adhesion to the flooring substrate.

Top Coat Formulation

The top coat formulation includes at least a coupling agent as definedherein, and can include an organic polymerizable monomer and/oroligomer, an inorganic polymerizable monomer, an appropriate solvent(typically an alcoholic solvent, such as methanol, ethanol, isopropylalcohol, propyl alcohol, and mixtures thereof.), and a polymerizationinitiator, for example, a photoinitiator. The formulation can alsoinclude hard particles, nanoparticles, surfactants, suspending andwetting agents, defoamers, etc., and other components typically found intop coat layers. Other polymerization initiators can be usedindependently or in combination with photoinitiators. These can includethermally-generated free radical initiators such as peroxides,peresters, etc., as well as cationic or anionic catalysts which canpolymerize the organic moiety of the coupling agent and/or the organicpolymerizable monomer. Additionally, compositions that can be cured bye-beam can be formulated without the need for initiators.

The top coat formulation can also include monomers with organicpolymerizable groups, for example, reactive diluents such as(meth)acrylates, epoxy resins, vinyl ethers, and the like. When thesemonomers are polymerized, they become incorporated into theorganic/inorganic layer along with the coupling agent.

The formulations can contain four components: (1) a poly alkyl metaloxide, e.g. tetraalkylorthosilicate (or tetraalkoxysilane), a hydrolyzedversion thereof and/or a partially hydrolyzed version thereof, (2) ametal alkoxide coupling agent, a hydrolyzed version thereof and/or apartially hydrolyzed version thereof, (3) an organic functionalgroup-containing (for example, epoxy and/or olefin-containing)polymerizable monomer and appropriate polymerization initiator, and,optionally, (4) a surfactant, for example, a nonionic surfactant such asa silicone surfactant. Poly metal oxides have the formula M(OR)n, whereR is, independently, an alkyl group, and where alkyl is a straight,branched or cyclic alkyl group, typically with between 1 and 10 carbonatoms, and n is equal or greater than 3.

The top coat layer can be prepared from the formulation using virtuallyany thin film application method, dried and cured. The resulting hybridfilm includes a chemically bonded metal oxide phase and polymer phase.Examples of compositions and methods for forming an organic/inorganictop coat layer are described, for example, in U.S. Pat. No. 5,120,811 toGlotfelter et al., the contents of which are hereby incorporated byreference in their entirety. Additionally, other examples oforganic/inorganic top coat compositions include those types described inU.S. Pat. Nos. 5,679,458; 5,647,941; 5,233,006; 5399,738; 5,414,093;5,674,964; 5,559,163; 4,644,077; 5,559,163; and 5,023,140, the contentsof which are hereby incorporated by reference in their entirety.

In one embodiment, the top coat formulation includes:

(a) an acid hydrolyzed tetraalkyl orthosilicate;

(b) an acid hydrolyzed silane-containing coupling agent;

(c) a difunctional organic-functional monomer with one or more olefinicand/or epoxy groups; and

(d) a photoinitiator.

One example of a composition of this type is:

(a) about 10 to about 70% of an acid-catalyzed hydrolysis product of atleast one silicate selected from tetramethylorthosilicate (TMOS),tetraethylorthosilicate (TEOS) and tetrapropylorthosilicate (TPOS);

(b) about 1 to about 70% acid-catalyzed epoxy/silane coupling agent;

(c) about 1 to about 70% of a difunctional, cycloaliphatic epoxy monomerhaving at least one cyclohexene oxide functionality;

(d) about 0.5 to about 10% of an photoinitiator capable of initiatingring-opening, cationic photopolymerization of (c); and

(e) about 0.1 to about 1% of a surfactant, for example, apoly(dimethylsiloxane) surfactant.

The individual components of the top coat formulation are discussed inmore detail below.

Coupling Agent

The coupling agent includes one or more organic polymerizable moietiesand one or more inorganic polymerizable moieties. The coupling agent caninclude, for example, two metal alkoxide moieties (upon acid hydrolysis)and two organic moieties. Additionally, the coupling agent can includethree metal alkoxide moieties and one organic moiety. The hydrolysisproduct of the metal alkoxides polymerize to provide the top coat layerwith inorganic character, and the organic polymerizable moieties can bepolymerized to provide the top coat layer with organic character.Examples of metal alkoxide moieties include aluminum alkoxide, zirconiumalkoxide, silicon alkoxide and titanium alkoxide moieties. The couplingagents can be dialkoxysilanes, trialkoxysilanes, and the like (andhydrolyzed or partially hydrolyzed versions thereof), provided they alsoinclude the organic polymerizable moieties.

The coupling agents can be derived from a number of readily availablemulti-functional organic compounds (i.e., compounds with functionalgroups, such as hydroxy, thiol, amine, carboxy, isocyanato, epoxy,(meth)acrylate, and the like). It is important that these functionalgroups can either polymerize/react with each other or polymerize/reactwith the polymerizable organic monomer which may be present in theformulation.

There are a number of commercially available silane coupling agents withpolymerizable functional groups. Examples include acrylates,methacrylates and epoxides which contain silanes. Examples of epoxygroups include glycidyl ether and cycloaliphatic oxides. One example ofan epoxy silane coupling agent is 3-glycidoxypropyltrimethoxy silane.

Inorganic Polymerizable Monomer

The inorganic polymerizable monomer is any inorganic moiety which can bepolymerized to form an inorganic polymer. As used herein, an inorganicpolymerizable moiety is a polymerizable group which, when polymerized,forms an inorganic polymer such as a glass. When present on the couplingagent, the moiety incorporates the coupling agent into a glass layerand/or forms a glass layer.

Silanols are an example of a metal oxide inorganic polymerizable moiety.Other metal alkoxides can be incorporated into glass layers and are alsoconsidered to be inorganic polymerizable moieties. Examples includetetraalkylsiloxanes, which can be partially and/or totally hydrolyzed,and mixtures of tetraalkylsiloxanes and partially and/or totallyhydrolyzed versions thereof. Examples of suitable tetraalkoxy silanesinclude tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS)and tetrapropylorthosilicate (TPOS), which, upon acid hydrolysis, becomeincorporated into the organic/inorganic layer along with the couplingagent.

Triethylborate (TEB) or boric acid may be substituted for the TMOS, TEOSor TPOS in amounts from 0.25 to 1.5% by weight of TMOS, TEOS or TPOS inorder to increase the useful lifetime of the coating solution. Othermetal alkoxides can be used to vary the properties of the wear surfaceprotective coating as long as they are compatible with the sol-gelprocess.

Basically, an alkyl-O-silane group is converted to an Si—O—H group byacid or base hydrolysis, and the Si—O—H groups polymerize to formSi—O—Si linkages. Each silicon atom in the polymer includes at least oneoxygen bond, and can include two, three or four oxygen bonds. Variousmetal alkoxides can also react with and become incorporated in theinorganic polymer. The coupling agents can cross link into the polymerif they include at least two such groups and can be incorporated intothe polymer network if they include at least one such group.

Additionally, colloidal metal oxide sols such as silica sols can be usedin combination with coupling agents to make organic/inorganic topcoatings. Examples include those described in U.S. Pat. Nos. 4,644,077and 5,559,163, the contents of which are hereby incorporated byreference in their entirety.

Organic Polymerizable Monomer/Oligomer

Organic polymerizable monomers are well known to those of skill in theart, and include an organic polymerizable moiety, for example, anolefinic group, an epoxy group, and the like. When the polymerizablemoieties are polymerized, they form an organic polymer. Similar moietiesin the coupling agent incorporate the coupling agent into and/or form anorganic polymer layer. Olefinic groups include vinyl ethers, vinyl,allyl, (meth)acrylate, acetylenic, etc.

As used herein, the distinction between monomers and oligomers is thatoligomers tend to include a plurality, typically more than about 2 andless than about 100, repeating units.

In one embodiment, the organic polymerizable monomer and/or oligomerincludes one or more reactive functional groups which polymerize undersimilar polymerization conditions as the polymerizable organic groups onthe coupling agent. In this embodiment, the monomer and/or oligomer canreact with the coupling agent while the organic portion of theorganic/inorganic top coat layer is being formed. However, in anotherembodiment, the organic reactive functional groups in the coupling agentand the monomer and/or oligomer can polymerize under different reactionconditions. An example of this is where an epoxy group is present in thecoupling agent and the monomer includes (meth)acrylate groups.

Examples of suitable epoxy monomers include ERL-4221 (Union Carbide),also known as CY-179 (Ciba-Geigy),3,4-epoxycyclohexyl-3,4-epoxycyclohexane carboxylate, ERL-4299 (UnionCarbide), also known as CY-178 (Ciba Geigy)-Bis(3,4- epoxy-6-methylcyclohexyl) adipate, ERL-4201 (Union Carbide)-3,4-epoxy-6-methylcyclohexanmethyl-3,4-epoxy-6-methylcyclohexane carboxylate, ERL-4206(Union Carbide), also known as RD-4 (CibaGeigy)-vinylcyclohexenedioxide, and DECO(Aldrich)-1,2,5,6-diepoxycyclooctane. A particularly useful epoxide isERL-4221 available from Union Carbide.

Vinyl monomers such as triethylene glycol divinyl ether can also provideexcellent gloss protection and stain resistance equivalent to the epoxymonomers. Acrylate or vinyl monomers such as described in U.S. Pat. Nos.2,760,863; 2,791,504; 2,927,022; 3,261,686; or 3,380,831, the contentsof which are hereby incorporated by reference, can be used solely or incombination with epoxy monomers depending on the degree of hardnessdesired for the protective coating.

Initiators

Photoinitiators

Mixtures of monomers may necessitate having mixtures of photoinitiatorsfor both cationic and free radical types of polymerization. Free radicalphotoinitiators such as benzoin ethers, benzophenone and the like arewell known to those of skill in the art. For cationic polymerization ofepoxy and other such groups there are commercially availablephotoinitiators which produce an acid catalyst capable of initiatingepoxy polymerization based on aryliodonium, arylsulfonium oraryldiazonium compounds. These include diphenyliodoniumhexafluorophosphate and bissulfide-bis-hexafluorophosphate.

Others

Other initiators can be employed to react the organic moieties of thecoupling agent and organic monomer materials. These can include wellknown thermal initiators that initiate free radical polymerization, orother catalysts for cationic or anionic polymerization/reaction of thecoupling agent moiety with the organic monomer, or the polymerization ofthe coupling agent and organic monomer. If the organic moieties arecross-linked via e-beam radiation, then no initiator may be required.The important factor is that the coupling agent is chemically reactedinto both organic and inorganic polymer networks.

Surfactants

A surfactant can be conveniently employed in the coating composition.Suitable surfactants include: Triton® X-100 from Rohm and Haas, Surfynol104E from Air Products, Aerosol OT from American Cyanamid, FC-120 from3M, and Tergitol NP-27 from Union Carbide. Examples include silicone oilsurfactants such as poly(dimethylsiloxane), which can provide the topcoat layer with superior stain and gloss protection.

Substrates

Substrates for flooring are well known in the art and include a solid,filled or unfilled polymeric layer or composite, a solid layer compositecomprising a fibrous web saturated with polymeric binder, and porousfibrous layers such as beater saturated felts, and non-woven fabricmaterials.

In one embodiment, the substrate comprises a PVC plastisol. In anotherembodiment, the substrate is a porous material. In an additionalembodiment, the substrate is a felt.

Flooring Structures

Flooring structures are also well known in the art and can includesingle or multiple layers in the form of tile or sheet. They can alsoinclude solid and foam layers. They can be made from melt processingtechniques, and in the case of PVC plastisols, wet coating processingtechniques. Flooring structures also mean any single or multiple layertypically used in flooring products. The flooring structures can includeone or more of a calendered polyvinyl chloride (PVC) layer, a foamablePVC plastisol layer and a design layer.

In one embodiment, the floor product includes a substrate of porous feltmaterial, a PET wear layer, an adhesion promoter overlying the PET wearlayer (i.e., a “primed” PET wear layer), and an organic/inorganic topcoat layer overlying the primed PET wear layer. The product can alsoinclude a flooring structure in contact with the felt layer, theflooring structure including a calendered PVC basecoat in direct contactwith the felt layer, a foamable PVC plastisol in contact with thebasecoat, and a design layer in contact with the foamable PVC plastisollayer.

In another embodiment, the floor product comprises a melt processed,filled resilient tile flooring structure, a PET wear layer, an adhesionpromoter on one surface of the PET wear layer in contact with the tileflooring structure, and additional adhesion promoter on the secondsurface of the PET wear layer, and an organic/inorganic top coat layeroverlying the second surface of the PET wear layer. The floor productcan be in the form of a tile or sheet material.

Sol Gel Transformation

The term polymerization is often used in sol-gel processing to describethe transformation of the sol phase to the gel/glass phase, since glassis a polymer. However, it is probably more correct to think of thegel-to-glass conversion as an aggregation step during which discreteoxide particles of small size (typically in the range of 4 nm for acidcatalyzed silicon alkoxides) form and are chemically bonded to oneanother. This contrasts with the molecular polymerization concept whereeach functional group is reacted to form either a linear or threedimensional network.

Glasses prepared from acid-catalyzed sol-gel processes form clear, hardfilms due to the extremely small sizes of the aggregated oxideparticles. Sol-gel derived glasses can rival the performance oftraditional glasses. Silicon alkoxides are by far the easiest alkoxidesfrom which such glasses can be formed. Tetraalkoxysilanes such astetraethylorthosilicate (TEOS) and tetramethylorthosilicate (TMOS) arereadily hydrolyzed at a pH of around 2 and condense upon evaporation ofsolvent to give approximately 90% yield of pure silica as determined byIR (powder dried 2 hrs. at 150C). If the hydrolysis product is left insolution and the solution sufficiently concentrated, a gel will form in24-72 hours. Optionally, glasses can also be obtained by basic catalysisof silicon alkoxides. The sol gel chemistry described herein applieswhether a coupling agent alone is used to prepare the sol gel glass, orwhether other inorganic polymerizable moieties are present.

The alkoxysilanes in the coupling agent present in the top coatformulation can be hydrolyzed by adding water and an acid catalyst. Theamount of water added determines the degree of hydrolysis in the finalproduct. The coupling agent can include a certain degree of hydrolyzedsiloxanes (i.e., siloxide groups).

The sol-gel processing conditions can be controlled to optimize variousphysical properties of the resulting glass. For example, one can controlthe particle size in the gels, which can optimize the optical clarity.The toughness of the glass can be varied, for example, by usingappropriate combinations of borosilicate, zirconia/silica and othermetal alkoxides. The organic monomers can be selected to provide hybridinorganic/organic materials with desired properties.

Generally, any of the metal alkoxides based upon Al, Zr, Si, or Ti willreadily form oxides after hydrolysis and solvent removal. Typically, theacid hydrolysis/condensation reactions of metal alkoxides are run usinga stoichiometric amount of water and at a pH of about 2. This procedureworks well for the silicon and aluminum alkoxides but other alkoxidessuch as zirconium and titanium can require a very low pH or slowhydrolysis reactions to maintain a reasonable stability.

Methods of Forming the Top Coat Layer

The general scheme for producing a polymer/glass hybrid is: (1)optionally preparing a hydrolyzed metal alkoxide in solution, (2)preparing a hydrolyzed coupling agent (i.e. bifunctional orpolyfunctional including at least one trialkoxysilane functionality andat least one polymerizable organic functionality) in solution, and aftermixing the above, (3) optionally including a polymerizable monomer, (4)including an appropriate initiator, (5) including a surfactant ifdesired, (6) coating on a clear, protective layer (7) drying, andpolymerizing the organic and inorganic networks. In one embodiment thepolymerization of the organic network is achieved by exposing the driedtop coat layer to a source of actinic radiation, for example,ultraviolet or e-beam energy.

In those embodiments where the top coat layer includes inorganic metaloxide polymerizable moieties such as tetraalkoxysilanes and organicpolymerizable moieties in addition to the coupling agent, the top coatlayer can be formed by:

(a) producing a hydrolyzed solution comprising:

-   -   (i) a metal alkoxide;    -   (ii) a coupling agent having at least one reactive organic        substituent;

(b) adding an organic monomer to the hydrolyzed solution, along with asuitable polymerization initiator;

(c) applying the composition in a dry thickness ranging between about 1and about 13 microns over a clear, polyethylene terephthalate wearlayer;

(d) drying the composition to remove solvent; and

(e) curing the composition.

The coating may be cured by any suitable means including heat orultraviolet light irradiation that is compatible with the reactivegroups in the top coat formulation and/or the polymerization initiator.

In another embodiment the inorganic portion of the organic/inorganiccomposition results from only the presence of the coupling agent.

In one embodiment the PET wear layer overlies a substrate such as atile, sheet flooring, table top, panel, or similar article ofmanufacturer before step c above is carried out. In another embodiment,the PET inorganic/organic composite film is laminated to a substrateafter it has been formed.

In some embodiments, the inorganic polymerizable and/or organicpolymerizable monomers can be absent from the coating composition. Inthese embodiments, the above steps can take place, without the presenceof these components.

In one embodiment, the organic/inorganic layer is formed by applying atop coat formulation including the acid-catalyzed hydrolysis product ofat least one silicate (i.e., tetramethylorthosilicate,tetraethylorthosilicate or tetrapropylorthosilicate), the acid-catalyzedhydrolysis product of an epoxy/silane coupling agent; and a suitableorganic monomer, to the PET wear layer. The inorganic portion of theorganic/inorganic layer is cured by removing the solvent and heating thetop coat layer. The organic portion of the organic/inorganic layer iscured by polymerizing the organic monomer. If the organic monomer is anolefin-containing material, the polymerization can involve exposure toactinic radiation, optionally in the presence of a photoinitiator. Ifthe organic monomer is an epoxy group, polymerization can be effectedusing any conventional initiator known to initiate polymerization ofepoxy groups, including initiators including thiol and/or hydroxygroups, as well as cationic catalysis which can include cationicphotoinititators.

Ideally, the organic functionality of the coupling agent and the organicfunctionality of the monomer are reactively compatible.

Methods for Improving Interlayer Adhesion

To function as a flooring material, the PET/(organic/inorganic)composite material must adhere to the substrate. Also, the PET wearlayer must adhere to the organic/inorganic top coat layer. Variousadhesion primers and surface treatments can be used to gain adhesion, ifrequired, and are selected based upon the substrate and flooringmaterial. These can include multilayer extruded or laminated PET films,or PET films with adhesion primer coating layers. PET film with adhesionpromoters are well known and commercially available. One preferred PETsupplier is DuPont Teijin Films who offer a wide variety of adhesionpromoters.

Methods of Applying the Composite Wear/Top Coat Layers

The wear/top coat layer can be applied by laminating a PET film to floorcovering component (including, for example, a substrate, foam layer anddesign layer). The top coat formulation can be subsequently applied byany convention means of application, the solvent evaporated to effectthe inorganic polymerization, and then the organic component subjectedto appropriate polymerization conditions, for example, UV cure.

In another embodiment, the method involves moving a substrate usingrolls adapted to carry the substrate, moving a PET film using rollsadapted to carry the PET film, wherein the substrate and the PET filmare heated and laminated together. The temperature, dwell time, and thepressure applied to the substrate/PET film composite are adjusted toprovide adhesion between the two layers after cooling. The interlayeradhesion can be improved, if necessary by applying an adhesion promoterto the substrate or the PET film before the PET film is applied.

An adhesion promoter can be applied to the PET film layer, if necessary,to promote adhesion to the organic/inorganic layer. Then, the top coatformulation can be applied and cured.

The substrate and the PET barrier layer film can be pre-heated beforecontacting each other, for example, using a radiator disposed adjacentto the path the substrate travels before it contacts the PET film. ThePET film itself can also be preheated using a radiator disposed adjacentto a path the PET film travels before it initially contacts thesubstrate.

In one embodiment, a PET wear layer film is laminated to a flooringstructure or substrate, the top coat layer applied over the PET wearlayer to form a floor covering component, or a completed flooringcovering. It is important is that the PET film layer have adequateadhesion to both the flooring structure/substrate and the top coatlayer.

In another embodiment, the PET film is coated with the inorganic/organictop coat layer and the composite film laminated to a flooring structureor substrate.

Referring to now to FIG. 1, showing a schematic drawing of a particularembodiment of the floor covering described herein, a typical flooringstructure 102 is illustrated that includes a felt substrate 104, acalendered PVC basecoat 106, a foamable PVC plastisol 108, an optionalclear PVC layer 109, a polyethylene terephthalate (PET) wear layer 110,and an organic/inorganic layer 112 adhered to the PET wear layer. ThePET wear layer 110 can include and an adhesion promoter on one or bothsurfaces.

Referring to FIG. 2, showing a schematic drawing of a particular tileembodiment of the floor covering described herein, a typical tilestructure is illustrated which includes a melt processed, calendaredfilled polymer tile layer such as Armstrong's Excellon Tile (100), apolyethylene terephthalate (PET) wear layer 110, and anorganic/inorganic layer 112 adhered to the PET wear layer. The PET wearlayer can include an adhesion promoter on one or both surfaces.

The following examples are intended to illustrate the invention and itis thought variations will occur to those skilled in the art.Accordingly, it is intended that the scope of the invention should belimited only by the appended claims.

EXAMPLES Example 1

An organically modified sol-gel formulation (O/I) as prepared in asimilar fashion to that described in Example 1 of U.S. Pat. No.5,120,811 was sprayed onto Dupont Teijin film (identified as Melinex617/500) that was pretreated with a proprietary acrylic polymer andtaped to a tile blank. The treated film taped to a tile carrier waspassed through an infrared oven ( Glenro) to remove solvent. The exitsurface temperature of the coated film/carrier was 137° F. Thisstructure was subsequently UV cured at a dose of 11. Joules/cm² to givegood cure. Coating thickness is estimated to be between 2-6 μms based onco-weights.

Using the flat bed press Wabash, the top platumin was heat to 310° F.and bottom left at 90° F. A sandwich was prepared in which thePET-organic/inorganic coated film sample was placed on a tile blank. Asmooth chrome plate placed on top of the coated film/tile and siliconpad on top of chrome plate. This structure was placed on top siliconbelt piece on top of a steel plate. The entire sandwich was placed inthe Wabash press and pressed at 20 tons for 3 to 5 minutes. The presswas opened and the sample allowed to cool prior to removal.

Table 1 contains comparative results for stain and gloss protection forthe invention versus uncoated tile. TABLE 1 30 Min. % gloss 60 Min. %gloss 90 Min. % gloss Test Sample retained retained retained Control 4627 17 Melinex 617/500 Invention 98 85 63

Example 2

Coatings were prepared as in Example 1 except that pretreated doubleside Melinex 582/400 film was used. 30 Min. % gloss 60 Min. % gloss 90Min. % gloss Test Sample retained retained retained Melinex 99 94 86582/400 invention

Example 3

Further benefit of this invention can be realized by the addition ofmicron size aluminum oxide to the thin hard coating. Coatings wereprepared as in Example 1 except that aluminum oxide having an averagesize of 0.2-0.4 microns ( Bawkowski E600) was added (10 gms/QtExample 1) and Melinex 725/500 was used. Tile samples were prepared inan identical fashion to that described in Example 1.

Table 3 contains comparative results for stain and gloss protection forthe invention versus uncoated tile. TABLE 3 30 Min. % gloss 60 Min. %gloss 90 Min. % gloss Test Sample retained retained retained Control 5131 21 Melinex 725/500 Invention 98 90 77 Example 2

Example 4

Samples of O/I (organic/inorganic) coated and uncoated Melinex films ontile were prepared as per Example 1, and subjected to Light Stabilitytesting using ASTM F1515-98. Data was obtained after 400 hours ofexposure and is listed in Table 1. TABLE 1 Xenon Test ASTM F1515-98Delta b Cool White Fluorescent T-626457 Tile Sample Xenon exposure(hours) 400 1 Melinex 617/500 Coated 1.262 5 Melinex 617/500 1.134 2Melinex 582/400 Coated 0.704 6 Melinex 582/400 1.311 3 Melinex 725/500Coated 1.925 7 Melinex 725/500 1.276 4 Melinex 6445/500 Coated 2.915 8Melinex 6445/500 2.754All simples showed little discoloration with Delta b values below 3units.

While specific embodiments have been set forth as illustrated anddescribed above, it is recognized that variations may be made withrespect to disclosed embodiments. Therefore, while the invention hasbeen disclosed in various forms only, it will be obvious to thoseskilled in the art that many additions, deletions and modifications canbe made without departing from the spirit and scope and no undue limitsshould be imposed except as set forth in the following claims.

1. A composite wear layer comprising: a) a polyethylene terephthalatewear layer; b) an organic/inorganic top coat layer, wherein theorganic/inorganic top coat layer is formed from a composition comprisinga coupling agent, an organic polymerizable monomer or oligomer and aninorganic polymerizable monomer, wherein the coupling agent is amolecule comprising an organic polymerizable moiety and an inorganicpolymerizable moiety, wherein the organic polymerizable moiety of thecoupling agent and the organic polymerizable monomer or oligomer areselected from the group consisting of (meth)acrylate, epoxy, isocyanate,vinyl ether, allyl, vinyl and acetylenic, wherein the organicpolymerizable moiety of the coupling agent is capable of reacting withthe organic polymerizable monomer or oligomer; and c) a first adhesionpromoter between the wear layer and the top coat layer. 2-7. (canceled)8. The composite wear layer of claim 1, wherein the wear layer comprisesa polyethylene terephthalate copolymer.
 9. The composite wear layer ofclaim 1, wherein the organic/inorganic top coat was formed from a topcoat formulation comprising a colloidal inorganic sol. 10-12. (canceled)13. The composite wear layer of claim 1, wherein the inorganicpolymerizable moiety is selected from the group consisting ofhydrolyzable Al, Zr, Si, Ti or B alkoxides and mixtures thereof. 14-18.(canceled)
 19. A surface covering or surface covering componentcomprising the composite wear layer of claim 1 and a substrate.
 20. Thesurface covering or surface covering component of claim 19, wherein thesurface covering or surface covering component is a floor covering orfloor covering component.
 21. The surface covering or surface coveringcomponent of claim 20, wherein the floor covering is a resilient tile.22. The surface covering or surface covering component of claim 20,wherein the floor covering is a resilient sheet product and wherein theresilient sheet product comprises a foam or foamable layer. 23-25.(canceled)
 26. The surface covering or surface covering component ofclaim 19, wherein a second adhesion promoter is between the wear layerand the flooring substrate.
 27. (canceled)
 28. The surface covering orsurface covering component of claim 26, wherein the second adhesionpromoter is different from the first adhesion promoter. 29-32.(canceled)
 33. A process of manufacturing a floor covering or floorcovering component, comprising: a) laminating a polyethyleneterephthalate film to a flooring substrate, b) applying a first adhesionpromoter to an exposed surface of the polyethylene terephthalate film,and c) applying an organic/inorganic top coat formulation to the exposedsurface of the adhesion promoter, wherein the organic/inorganic top coatlayer is formed from a composition comprising a coupling agent, anorganic polymerizable monomer or oligomer and an inorganic polymerizablemonomer, wherein the coupling agent is a molecule comprising an organicpolymerizable moiety and an inorganic polymerizable moiety, wherein theorganic polymerizable moiety of the coupling agent and the organicpolymerizable monomer or oligomer are selected from the group consistingof (meth)acrylate, epoxy, isocyanate, vinyl ether, allyl, vinyl andacetylenic, wherein the organic polymerizable moiety of the couplingagent is capable of reacting with the organic polymerizable monomer oroligomer. 34-35. (canceled)
 36. The process of claim 33, wherein asecond adhesion promoter is between the wear layer and the flooringsubstrate.
 37. (canceled)
 38. The process of claim 36, wherein thesecond adhesion promoter is different from the first adhesion promoter.39. The process of claim 33, wherein the polyethylene terephthalate filmcomprises a copolymer of polyethylene terephthalate.
 40. A process ofmanufacturing a floor covering or floor covering component, comprising:a) applying, an organic/inorganic top coat formulation to a polyethyleneterephthalate film, wherein the organic/inorganic top coat layer isformed from a composition comprising a coupling agent, an organicpolymerizable monomer or oligomer and an inorganic polymerizablemonomer, wherein the coupling agent is a molecule comprising an organicpolymerizable moiety and an inorganic polymerizable moiety, wherein theorganic polymerizable moiety of the coupling agent and the organicpolymerizable monomer or oligomer are selected from the group consistingof (meth)acrylate, epoxy, isocyanate, vinyl ether, allyl, vinyl andacetylenic, wherein the organic polymerizable moiety of the couplingagent is capable of reacting with the organic polymerizable monomer oroligomer, and b) laminating the composite wear layer to a flooringsubstrate such that the polyethylene terephthalate film is overlying theflooring substrate and the organic/inorganic top coat is exposed. 41.The process of claim 40, wherein the polyethylene terephthalate filmfurther comprises an adhesion promoter and the top coat formulation isapplied to the adhesion promoter.
 42. (canceled)
 43. The process ofclaim 40, wherein a second adhesion promoter is between the wear layerand the flooring substrate.
 44. (canceled)
 45. The process of claim 43,wherein the second adhesion promoter is different from the firstadhesion promoter.
 46. The process of claim 40, wherein the polyethyleneterephthalate film comprises a copolymer of polyethylene terephthalate.47. The surface covering or surface covering component of claim 19,wherein the polyethylene terephthalate wear layer comprises a copolymerof polyethylene terephthalate.